Paper

The pulp and paper industry produces a wide variety of primary products, including newsprint, printing and writing papers, packaging and industrial papers, corrugated containers, gray and bleached boxboards, bags, dissolving pulps, and wood pulp. All pulping processes involve tremendous amounts of water and timber.

Background

Before the invention of paper, written words were preserved on fabric in the form of scrolls. The Chinese are credited with inventing paper around 105 c.e. Historians note that this date was chosen somewhat subjectively, as early experiments in the process of papermaking probably stretched over a long period of time before the process was perfected. No records exist that indicate how the Chinese first made paper, but it is believed that this early paper was made by pouring fibrous pulp onto flat cloth-covered molds, then drying it—essentially the same way paper is produced today. Once the pulp had dried, an interlocking matrix of fibers created the paper. Early forms of paper were not as well processed as modern paper products. In fact, early forms of paper had more in common with the fabrics they replaced than with modern paper. They were coarse in nature, but they did lie flat. This quality made it possible for the first real books to be produced.

Over the following five hundred years, the Chinese papermaking process slowly spread throughout Asia, from Vietnam and Tibet to Korea and eventually to Japan in the sixth century. The Japanese refined the process and continued to produce high-quality paper varieties for centuries. The process moved west through Nepal and India. Several papermaking devices were captured by Islamic warriors, thus moving the technology further west through the Muslim world. It went to Baghdad into Egypt and across North Africa. The technology finally entered Europe in the twelfth century when the Moors invaded Spain and Portugal.

In 1456, the German printer Johannes Gutenberg successfully printed a Bible on his movable-type press, making it possible for the written word to move out to a much larger population. Industrial papermaking and printing grew from this point.

The Fourdrinier Machine

The first major improvement in papermaking was dipping the molds directly into the fibrous pulp (the exact date of this improvement is unknown). Dipping the molds allowed artisans to produce a greater quantity of high-quality paper.

Paper was made by hand until the early nineteenth century, when the Fourdrinier brothers, Henry and Sealy, introduced the first machine designed specifically for the manufacture of paper. The Fourdrinier brothers were the financiers of the first modern papermaking machine, which was designed by Nicholas Louis Robert in Essonnes, France. Robert received a patent for the continuous papermaking machine in 1799. Unable to afford the cost of development and implementation of his machine, Robert and his partner, Saint-Léger Didot (who often claimed the continuous papermaking machine was of his own invention), sent Didot’s brother-in-law, John Gamble, to England to find financial backing. A British patent was awarded in October, 1801. The first continuous paper machine was installed and made operational in Hertfordshire, England, in 1803. The next year, another machine followed. Robert sold the rights to his invention to the Fourdrinier brothers in England. The principle of Robert’s machine was to construct the paper on an extensive woven-wire cloth that retained the matted fibers while allowing the excess water to drain through—this same principle holds with all modern papermaking machines.

In the United States, the first documented papermaking machine was installed in 1817, in Brandywine Creek, Delaware, by the Thomas Gilpin Mills. This machine differed from the Fourdrinier device in that it was a cylindrical mold. The first Fourdrinier device was installed in the United States in 1827.

Production of Pulp and Paper

Paper production has changed significantly since the early industrial days and even the boom manufacturing years of the 1960s and 1970s. The recycling of paper products has become commonplace, as have government-mandated levels of postconsumer fiber content. A single sheet of paper could contain fibers from hundreds of different trees around the world. These fibers travel thousands of kilometers from the forest to the office printer. While recycling technologies have greatly improved in the twenty-first century, there is still only a 10 percent chance that the common paper used in personal printers contains postconsumer recycled fibers. On average, office employees in the United States use almost ten thousand sheets of paper, roughly 12 kilograms of paper per person per year. In 2005, the average North American created 302 kilograms of paper waste per year compared to 231 kilograms for citizens of high-income countries other than the United States and Canada, or 39 kilograms for citizens of middle-income countries, or 4 kilograms for citizens of low-income countries.

The manufacturing of paper and paperboard involves the production and conversion of pulp from some fibrous furnish. “Furnish” is any blend of fibrous materials (such as timber, wood chips, or recycled paper) used to produce pulp. Wood is the most commonly used furnish—roughly 95 percent of all pulp and paper manufacturers use wood in some form. The second most widely used form of furnish is secondary fibers from either mill waste or postconsumer fibers, such as newsprint and corrugated boxes. The usage of secondary fibers grows as consumer and commercial demand increases for products made from recycled paper.

Pulp Production

The production of pulp once involved the breaking down of homogeneous furnish feedstock into its fibers, often bleaching to increase the whiteness of the paper fibers, and mixing with water to produce a slurry. In August, 1998, the Environmental Protection Agency (EPA) passed a regulation called the cluster rule. This rule requires the pulp industry to stop the use of bleaches in paper production and imposes the use of chlorine-free colorants instead. These chlorine dioxide derivatives are created from sodium chlorate instead of chlorine. A totally chlorine-free future is being sought by the EPA for paper production in the United States and other countries.

There are four types of pulping processes: chemical, semichemical, mechanical, and secondary fiber pulping. Chemical pulping includes the kraft (sulfate) process, soda pulping, sulfite pulping, and neutral sulfite chemical pulping. Mechanical pulping includes chemi-mechanical, thermo-mechanical, chemi-thermo-mechanical, refiner mechanical pulping, and stone groundwood pulping. The type of pulping process affects the durability, appearance, and intended use of the resulting paper product. Regardless of the pulping method employed, pulping is “dirty.” During the pulping stage of production, nuisance odors may be released into the air, and dioxins from kraft chemical bleaching may be released into wastewater. Thus the pulping process is a major concern to the EPA in the United States and equivalent agencies in Europe.

Chemical pulping liberates the fibers from the furnish by dissolving the lignin bonds, which hold the cellulose fibers together, by cooking wood chips in liquid chemical solutions at extremely high temperatures and pressures. Kraft pulping is by far the dominant form of chemical (and nonchemical) pulping because of its early development in the 1800s, its ability to use nearly every species of wood as furnish, and the fact that its resulting pulps are stronger than those of other chemical processes. However, chemical pulp yields are roughly 45 to 50 percent. In other words, roughly 50 percent of the furnish is converted into pulp.

Semichemical pulping produces very stiff pulp and is used mainly for corrugated containers. The semichemical process consists of the partial digesting of hardwood furnish in a diluted chemical solution before it is mechanically refined to separate the fibers from the weakened furnish. Pulp yields range between 55 percent and 90 percent, depending on the process employed.

Mechanical pulping processes involve the reduction of furnish to fiber by either beating or grinding. This is the oldest known method of releasing the cellulose fibers from wood furnish. The pulp yields are high, up to 95 percent, especially when compared with chemical pulping yields of 45 to 50 percent. However, the mechanically produced pulp is of low strength and quality. Thus, mechanical pulp is often combined with chemical pulp to increase both its strength and quality.

Finally, secondary fiber pulping relies on recovered (recycled) papers as furnish. Typically, secondary fibers are presorted and preprocessed before they are sold to a pulp and paper mill. If the recovered papers have not been preprocessed, then they must first be treated to remove common contaminants, such as adhesives, coatings, inks, and dense plastic chips. The most common technique of secondary fiber pulping involves mixing the recycled furnish in a large container of water, which is sometimes heated. Pulping chemicals may be added to induce the dissolution of paper or paperboard. The mix is then stirred by a rotor to produce the pulp.

Pulping processes involve tremendous amounts of water, and most require large amounts of timber. Of all the wood harvested globally for industrial purposes, 42 percent goes into the production of paper. Latin America is a growing supplier of harvested wood for paper manufacturing. Furthermore the international Organization of Economic Cooperation and Development indicates that paper and pulp industries are the largest consumers of water of all the major industrial sectors. The papermaking process generates large amounts of air and water pollutants, especially during the pulping stage. It ranks third behind the chemical and steel industries in greenhouse emissions. In 2000, the world’s largest producers of paper pulp were the United States, at 57,002 metric tons, and Canada, at 26,411 metric tons, followed by China, Finland, Sweden, Japan, Brazil, Russia, Indonesia, and Chile.

Manufacturing Paper

There are two general steps in the process of making paper and paperboard: wet-end operations and dry-end operations. During the wet-end operations, processed pulp is transformed into a paper product via a paper machine, the most common of which is the Fourdrinier paper machine.

Pulp slurry (more than 90 percent water at the start) is deposited on a rapidly moving wire mesh for removal of the water by gravity, vacuum chambers, and vacuum rolls. After vacuum rolling, a continuous sheet is left, which is then pressed between a progression of rollers to extract any additional water and to compress the fibers. The sheet is then ready for dry-end operations. During this stage, the sheet enters a drying area, where the paper fibers start to bond as they are compressed by steam-heated rollers. The sheets are then pressed between massive rollers to reduce paper thickness and to produce a smooth surface. After a smooth thin sheet of paper is produced, coatings may be applied to improve the color, luster, printing detail, and brilliance. Finally, the paper product is spooled for storage.

From there, the process of bringing the consumer a standard 8.5-inch-by-11-inch sheet of paper involves nothing more than loading the spool of oversized paper onto a machine and slitting it down to size. Large mechanical guillotine cutters that operate at incredibly high speeds cut the mother sheet into smaller segments and the finished sized sheets are delivered to the packaging department, then sent on to the consumer. In 2014, China and the United States were the top paper consumers globally. They were followed by Japan, Germany, India, and Italy. China was also the world’s largest producer of paper and related products in 2014. Although paper consumption decreased in the United States, paper consumption increased throughout the world. In 2015, a study showed that paper production is the third most energy-intensive of all manufacturing industries.

All of this papermaking is not without its ecological drawbacks. Paper and paperboard packaging is the single largest component of American municipal solid waste. While these items are easily recycled, they are not being recycled as prevalently as they should be. There is still much work to be done in educating the public on the importance of recycling paper and paper products, not the least of which is the reduction of landfill size.

Bibliography

“29 Insane Paper Consumption Statistics,” BrandonGaille, brandongaille.com/29-insane-paper-consumption-statistics/. Accessed 24 Feb. 2017.

Biermann, Christopher J. Handbook of Pulping and Papermaking. 2d ed. San Diego, Calif.: Academic Press, 1996.

“Consumption of Paper and Paperboard in Selected Countries Worldwide in 2014 (in 1,000 Metric Tons).” Statista, www.statista.com/statistics/240565/consumption-volume-of-paper-and-paperboard-in-selected-countries/. Accessed 24 Feb. 2017.

Gray, Wayne B. Productivity Versus OSHA and EPA Regulations. Ann Arbor, Mich.: UMI Research Press, 1986.

Holik, Herbert, ed. Handbook of Paper and Board. Weinheim, Germany: Wiley, 2006.

Hunter, Dard. Papermaking: The History and Technique of an Ancient Craft. 2d ed., rev. and enlarged. New York: A. A. Knopf, 1947. Reprint. New York: Dover Publications, 1978.

Joint Textbook Committee of the Paper Industry. Pulp and Paper Manufacture. 2d ed. Edited by Ronald G. Macdonald and John N. Franklin. New York: McGraw-Hill, 1969.

Smith, David C. History of Papermaking in the United States, 1691-1969. New York: Lockwood, 1971.

Smith, Maureen. The U.S. Paper Industry and Sustainable Production: An Argument for Restructuring. Cambridge: Massachusetts Institute of Technology Press, 1997.

Thorp, Benjamin A., and M. J. Kocurek, eds. Paper Machine Operations. Pulp and Paper Manufacture, Series Seven. 3d ed. Atlanta, Ga.: Joint Textbook Committee of the Paper Industry, 1991.

Tillman, David A. Forest Products: Advanced Technologies and Economic Analyses. Orlando, Fla.: Academic Press, 1985.

U.S. Environmental Protection Agency Office of Enforcement and Compliance Assurance. EPA Office of Compliance Sector Notebook Project: Profile of the Pulp and Paper Industry. 2d ed. Washington, D.C.: U.S. Government Printing Office, 2002.